1. Field of the Invention
The present invention relates to a semiconductor device in which ESD is less likely to occur in a manufacturing process and a manufacturing method thereof.
In this specification and the like, the semiconductor device refers to any device which can function by utilizing semiconductor characteristics; an electro-optical device, a display device, a semiconductor circuit, and an electronic device are all included in the category of the semiconductor device.
2. Description of the Related Art
In a semiconductor circuit used in a semiconductor device such as a display device, a semiconductor element, an electrode, an insulating layer, or the like could be damaged by electrostatic discharge (hereinafter referred to as “ESD”). As a measure to prevent damage of a semiconductor circuit due to ESD, a protection circuit is connected to a semiconductor circuit in many cases. A protection circuit refers to a circuit for preventing overvoltage applied to a terminal, a wiring, or the like from being supplied to a semiconductor circuit. A resistor, a diode, a transistor, and a capacitor are typically used in the protection circuit.
Even when noise as well as a signal and power supply voltage is input to a wiring or the like, the protection circuit can also prevent a malfunction of a semiconductor circuit in a later stage due to the noise and degradation or damage of the semiconductor element due to the noise.
Patent Document 1, for example, discloses a technique of connecting a protection circuit in which a MOS transistor whose source and gate are short-circuited and a MOS transistor whose gate and drain are short-circuited are connected in series between a scan electrode of a display device and a conductive line provided in the periphery of a display portion.